dictyNews Electronic Edition Volume 35, number 18 Dec 17, 2010 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to dicty@northwestern.edu or by using the form at http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit. Back issues of dictyNews, the Dicty Reference database and other useful information is available at dictyBase - http://dictybase.org. Follow dictyBase on twitter: http://twitter.com/dictybase HAPPY HOLIDAYS AND A JOYOUS NEW YEAR! ========= Abstracts ========= Sex Determination in the Social Amoeba Dictyostelium discoideum Gareth Bloomfield, Jason Skelton, Alasdair Ivens, Yoshimasa Tanaka, Robert R. Kay Science, in press The genetics of sex determination remain mysterious in many organisms, including some that are otherwise well studied. Here we report the discovery and analysis of the mating-type locus of the model organism Dictyostelium discoideum. Three forms of a single genetic locus specify this species' three mating types: two versions of the locus are entirely different in sequence, and the third resembles a composite of the other two. Single, unrelated genes are sufficient to determine two of the mating types, whereas homologs of both these genes are required in the composite type. The key genes encode polypeptides that possess no recognizable similarity to established protein families. Sex determination in the social amoebae thus appears to use regulators that are unrelated to any others currently known. Submitted by Gareth Bloomfield [garethb@mrc-lmb.cam.ac.uk] -------------------------------------------------------------------------------- Quick guide Dictyostelium Louise Fets, Rob Kay, and Francisco Velazquez Cell Biology Division, MRC-Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK. Current Biology, 7 December, 2010, Volume 20, Issue 23 The Quick guide answers the following questions: What is Dictyostelium? How can an amoeba be ÔsocialÕ? So how do the cells move? How do the amoebae know where to go? What can we learn from its development? Can Dicty be used for medical research? What techniques can be used with Dicty? What resources are there? Anything else? Where can I find out more? Submitted by: Francisco Velazquez [fv@mrc-lmb.cam.ac.uk] -------------------------------------------------------------------------------- Developmental Changes in Transcriptional Profiles William F. Loomis 1 and Gad Shaulsky 2 1. Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093 2. Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030. Devel. Growth & Differ., in press Recent advances in quantitation of mRNA by hybridization to microarrayed gene sequences or by deep sequencing of cDNA (RNA-seq) have provided global views of the abundance of each transcript. Analyses of RNA samples taken at 2 or 4 hour intervals throughout development of Dictyostelium discoideum have defined the developmental changes in transcriptional profiles. Comparisons of the transcriptome of wild-type cells to that of mutant strains lacking a gene critical to progression through the developmental stages have defined key steps in the progression. The transcriptional response to cAMP pulses depends on the expression of pulse-independent genes that have been identified by transcriptional profiling with microarrays. Similar techniques were used to discover that the DNA binding protein GBF functions in a feed-forward loop to regulate post-aggregation genes and that expression of a set of late genes during culmination is dependent on the DNA binding protein SrfA. RNA-seq is able to reliably measure individual mRNAs present as a single copy per cell as well as mRNAs present at a thousand fold higher abundance. Using this technique it was found that 65% of the genes in Dictyostelium change two fold or more during development. Many decrease during the first 8 hours of development while the rest increase at specific stages and this pattern is evolutionarily conserved as found by comparing the transcriptomes of D. discoideum and D. purpureum. The transcriptional profile of each gene is readily available at dictyBase and more sophisticated analyses are available on DictyExpress. Submitted by Bill Loomis [wloomis@ucsd.edu] -------------------------------------------------------------------------------- FYVE-Dependent Endosomal Targeting of an Arrestin-Related Protein in Amoeba Dorian Guetta1,2,3, Karine Langou1, Didier Grunwald3,4,5, Gerard Klein1,2,3, Laurence Aubry1,2,3 1 CEA, DSV, iRTSV, Laboratoire de Biochimie et Biophysique des Systemes Integres, Grenoble, France, 2 LBBSI, UMR5092 CNRS, Grenoble, France, 3 Universite Joseph Fourier, Grenoble, France, 4 CEA, DSV, iRTSV, Lab. Transduction du Signal, Grenoble, France, 5 LTS, EMI104 INSERM, Grenoble, France PLOS One, online Background: Visual and beta-arrestins are scaffolding proteins involved in the regulation of receptor-dependent intracellular signaling and their trafficking. The arrestin superfamilly includes several arrestin domain-containing proteins and the structurally related protein Vps26. In Dictyostelium discoideum, the arrestin-domain containing proteins form a family of six members, namely AdcA to -F. In contrast to canonical arrestins, Dictyostelium Adc proteins show a more complex architecture, as they possess, in addition to the arrestin core, other domains, such as C2, FYVE, LIM, MIT and SAM, which potentially mediate selective interactions with either lipids or proteins. Methodology and Principal Findings: A detailed analysis of AdcA has been performed. AdcA extends on both sides of the arrestin core, in particular by a FYVE domain which mediates selective interactions with PI(3)P, as disclosed by intrinsic fluorescence measurements and lipid overlay assays. Localization studies showed an enrichment of tagged- and endogenous AdcA on the rim of early macropinosomes and phagosomes. This vesicular distribution relies on a functional FYVE domain. Our data also show that the arrestin core binds the ADP-ribosylation factor ArfA, the unique amoebal Arf member, in its GDP-bound conformation. Significance: This work describes one of the 6 arrestin domain-containing proteins of Dictyostelium, a novel and atypical member of the arrestin clan. It provides the basis for a better understanding of arrestin-related protein involvement in trafficking processes and for further studies on the expanding roles of arrestins in eukaryotes. Submitted by Laurence Aubry [laubry@cea.fr] ============================================================== [End dictyNews, volume 35, number 18]